More than half the states have now been excused from important conditions of the No Child Left Behind education law, the New York Times reports. They’ve been allowed to create new measures of how much students have improved and how well they are prepared for college or careers, and to assess teacher performance on that basis. Teachers will be evaluated in part on how well their students perform on standardized tests. One study, though, found that some state plans could weaken accountability. How can we measure achievement of students, teachers and schools in a way that is fair and accurate, and doesn’t provide incentives for obsessive testing, and cheating?